Polymers of fluorinated dioxoles

ABSTRACT

Fluorinated dioxole compounds and the process of preparation are disclosed which compounds are of the formula ##EQU1## wherein R 1  and R 2  are both perhalogenated hydrocarbon radicals of 1 to 3 carbon atoms containing at least one fluorine atom. The compounds may be homopolymerized and copolymerized for casting into films or yielding molded articles.

RELATED APPLICATION

This is a division of application Ser. No. 384,498, filed Aug. 1, 1973,now U.S. Pat. No. 3,865,845, which is a continuation-in-part ofcopending patent application Ser. No. 118,559, filed Feb. 24, 1971, nowabandoned.

The present invention relates to a new class of dioxole compounds. Moreparticularly, the present invention is directed to a novel class offluorinated dioxole compounds and a process for their preparation.

According to the present invention there is provided a new class offluorinated dioxole compounds of the general formula: ##STR1## whereinR₁ and R₂ are the same or different each having 1 to 3 carbon atomswhich are perhalosubstituted and contain at least one fluorine atom.

Preferably, both R₁ and R₂ are identical and fully perfluorinated.However, it is within the scope of this disclosure that in theperhalosubstitution a halogen such as chlorine be employed in additionto fluorine. An illustrative example is when both R₁ and R₂ denote CF₂Cl. An illustrative example with R₁ and R₂ differing is R₁ denoting CF₂Cl and R₂ denoting CF₃.

Perhalosubstituted and perfluorinated are employed in their normaldefinition and denote the substitution on the carbon atom(s) is limitedrespectively to halogen and fluorine.

A most preferred embodiment of the fluorinated dioxole compounds of theinvention is perfluoro-2,2-dimethyl-1,3-dioxole of the formula ##STR2##

According to the present invention there is also provided a process forpreparing the novel class of compounds of formula (1) above whichcomprises dehalogenating a fluorinated dioxolane of the general formula##STR3## wherein R₁ and R₂ are as above defined and R₃ and R₄ arehalogen other than fluorine, in an organic solvent in the presence ofmagnesium.

The novel fluorinated dioxole compounds of the invention are clear,colorless liquids. Also, the perfluoro-2,2-dimethyl-1,3-dioxole of theinvention has a boiling point of about 33°C.

A surprising and unexpected property of the novel class of compounds ofthe invention is that they may be homopolymerized or copolymerized. Thehomopolymerization or copolymerization may be undertaken with standardtechniques well known in the art. Additionally,perfluoro-2,2-dimethyl-1,3-dioxole homopolymerizes on standing after 2to 5 days duration. Form the copolymerization, conventional monomerswell known in the art may be employed. Illustratively, the monomersdisclosed in U.S. Pat. No. 2,468,664 are suitable in forming thecopolymer. Highly desirable comonomers include chlorotrifluoroethylene,vinylidene fluoride and and hexafluoropropene.

The homopolymers and copolymers may be cast into films or molded byconventional techniques.

The process for preparing the above-described fluorinated dioxolecompounds of the invention is exemplified herebelow, and in typicalpractice includes adding a fluorinated dioxolane of formula (3) above toa heated mixture of magnesium in anhydrous tetrahydrofuran. Theperfluoro dioxole may be recovered from the resulting mixture by anysuitable means such as distillation.

The reaction is highly exothermic and may be conducted at any suitabletemperature. Preferably, the reaction mixture is initially heated at atemperature below about 65°C. Also, the reaction may be conducted at anysuitable pressure; preferably, the reaction is conducted at atmosphericpressure or at a pressure below atmospheric pressure.

The principle and practice of the present invention will now beillustrated by the following Examples which are only exemplary thereofand it is not intended that the invention be limited thereto sincemodifications in technique and operation will be apparent to anyoneskilled in the art.

The starting dioxolanes for the preparation of ##STR4## may be preparedfollowing the general methods described in U.S. Pat. No. 2,925,424 andon page 44 of the December 1970 issue of the Product Licensing Indexpublication.

For example, [R₁ = CF₃ ; R₂ = CF₂ Cl] reaction ofchloropentafluoroacetone with 2-chloroethanol followed by treatment withpotassium carbonate yields 2-chlorodifluoromethyl-2-trifluoromethyl-1,3-dioxolane. Chlorination at 50°C. with chlorine andcarbon tetrachloride yields2-chlorodifluoromethyl-2-trifluoromethyl-4,4,5,5-tetrachloro-1,3-dioxolane.Fluorination with SbF₃ /SbCl₅ at 120° yields2-chlorodifluoromethyl-2-trifluoromethyl4,5-dichloro-4,5-difluoro-1,3-dioxolane, the starting dioxolane for thepreparation of2-trifluoromethyl-2-chlorodifluoromethyl-4,5-difluoro-1,3-dioxole. Theuse of other starting ketones e.g., sym dichlorotetrafluoroacetone,perfluorodiethyl ketone, perfluoromethylethyl ketone yields dioxoleswith differing R₁ and R₂.

More specifically, perfluoro-2,2-dimethyl-4,5-dichloro-1,3-dioxolaneutilized in the examples herebelow may be prepared by the methoddisclosed on page 44 of the December, 1970 issue of the ProductLicensing Index publication which described that the above-mentioneddioxolane may be obtained fluorinating2,2-bis(trifluoromethyl)-4,4,5,5-tetrachloro-1,3-dioxolane with SbF₃--SbCl₅ at 120°C. The2,2-bis(trifluoromethyl)-4,4,5,5-tetrachloro-1,3-dioxolane may beprepared in accordance with the method described in U.S. Pat. No.2,925,424.

EXAMPLE 1 -- PREPARATION OF PERFLUORO-2,2-DIMETHYL-4,5-DIBROMO-1,3-DIOXOLANE

A 50/50 mixture of perfluoro-2,2-dimethyl-1,3-dioxole andperfluoro-2,2-dimethyl-4,5-dichloro-1,3-dioxolane was cooled in an icebath while being irradiated with a sun lamp. Bromine was added dropwiseand an immediate exothermic reaction took place. Bromine addition wascontinued until the bromine no longer reacted and the brown color ofbromine remained. The reaction mixture was washed with 5% aqueous sodiumbisulfite and dried. A gas chromatogram of the crude product showed itto be a 50/50 mixture ofperfluoro-2,2-dimethyl-4,5-dichloro-1,3-dioxolane and a higher boilingmaterial. Distillation of the crude product yielded in addition toperfluoro-2,2-dimethyl-4,5-dichloro-1,3-dioxolane, boiling at 86°, acolorless liquid, b.p. 116°. A gas chromatogram of the liquid showed itto be approximately 97 percent pure. The infrared spectrum of the liquidwas consistent with the structure,perfluoro-2,2-dimethyl-4,5-dibromo-1,3-dioxolane. The NMR spectrum ofanother sample prepared by the same procedure was also consistent withthis structure.

PREPARATION OF PERFLUORO-2,2-DIMETHYL-1,3-DIOXOLE

A mixture of 15 g. of absolute ethanol, 2.0 g. of zinc dust and 3.5 g.of perfluoro-2,2-dimethyl-4,5-dibromo-1,3-dioxolane was added to athoroughly dried 50 ml. 3-necked flask fitted with a magnetic stirrer,dropping funnel and small distillation column topped by a Dry Ice cooledtrap. The reaction mixture was stirred and heated to give 5 ml. ofdistillate in addition to material in the Dry Ice cooled trap. Thedistillate separated into an upper and a lower layer when added to icewater, and the lower layer was recovered and added to the trap materialto give 0.62 g. of product. A gas chromatogram of this product showed itto consist of 63 percent of material having a retention time identicalto authentic perfluoro-2,2-dimethyl-1,3-dioxole. An infrared spectrum ofthis 63 percent of the product was identical to that ofperfluoro-2,2-dimethyl-1,3-dioxole.

EXAMPLE 2

7.3 Grams of magnesium turnings, 100 ml. of anhydrous tetrahydrofuranand one crystal of iodine was added into a dry and nitrogen flushed 200ml. capacity round bottom flask having three openings and equipped witha magnetic stirrer, a pressure equalizing dropping funnel, a thermometerand a take-off head with a Dry Ice cooled trap. The mixture was stirredand heated to 60°C. and then a solution of 20 grams ofperfluoro-2,2-dimethyl-4,5-dichloro- 1,3-dioxolane in 20 mls. ofanhydrous tetrahydrofuran was slowly added to the flask. A vigorousreaction took place and 25 mls. of distillate boiling between 33°C. and65°C. was distilled from the reaction mixture. The distillate was pouredinto cold water and the mixture separated into two layers. The lowerlayer was recovered and dried and the resulting product was combinedwith the material in the Dry Ice cooled trap; 9.1 grams of product wasobtained. The latter was distilled using a 2 foot spinning band column,and a center cut having a boiling point of 33°C. was extracted which wasperfluoro-2,2-dimethyl-1,3-dioxole of greater than 98 percent purity.The mass spectrum of the product exhibited a strong peak at m/e of 244which is consistent with that of perfluoro-2,2-dimethyl-1,3-dioxole.

EXAMPLE 3

2.0 Grams of perfluoro-2,2-dimethyl-1,3-dioxole dissolved in 100 ml. of(Freon 113), 25 mls. of an 0.001 percent solution of perfluoropropionylperoxide in Freon 113 and 10 grams of tetrafluoroethylene was added to astainless steel autoclave of 180 mls. capacity. The mixture was heatedat 50°C. for 2 hours. A yield of 2.5 grams of a white, solid polymericproduct was obtained. The product exhibited a broad endothermic peakwhen subjected to Differential Thermal Analysis (using a Du Pont Model900 DTA apparatus) indicative of a melting point about 265°C. Aninfrared spectrum scan of the copolymer product showed the presence of astrong band at 10.1 microns due to a perfluoroether group.

EXAMPLE 4

A sample of perfluoro-2,2-dimethyl-1,3-dioxole prepared by the methodshown in Example 2 was washed with water and dried with calciumchloride. The sample, 5.0 g., was allowed to stand at room temperaturein a Dry Box in a nitrogen atmosphere. It polymerized on standing togive a clear solid which was pressed into a film whose infrared spectrumwas consistent with that of polyperfluoro-2,2-dimethyl-1,3-dioxole.

EXAMPLE 5

A 0.8 g. sample of perfluoro-2,2-dimethyl-1,3-dioxole was sealed in aquartz tube and irradiated with 16 RPR-2537A lamps in aSrinivasan-Griffin Photochemical Reactor (Southern New EnglandUltraviolet Co., Middletown, Conn.) for 64 hours. The product was ayellowish solid whose IR spectrum in Freon C51-12 was consistent withthe polyperfluoro-2,2-dimethyl-1,3-dioxole structure.

Although the invention has been described by way of specificembodiments, it is not intended to be limited thereto. As will beapparent to those skilled in the art, numerous embodiments can be madewithout departing from the spirit of the invention or the scope of thefollowing claims.

What is claimed is:
 1. A copolymer of fluorinated dioxole of the formula##EQU2## wherein R₁ and R₂ are the same or different both consisting of1 to 3 carbon atoms which are perhalosubstituted and containing at leastone fluorine atom whereby the perhalosubstitutuents are selected fromthe group consisting of chlorine and fluorine atoms and a comonomerselected from the class consisting of chlorotrifluoroethylene,vinylidene fluoride and hexafluoropropene.
 2. The polymer of claim 1wherein both R₁ and R₂ contain one carbon atom.
 3. The polymer of claim2 wherein R₁ and R₂ are different.
 4. The polymer of claim 1 whereinsaid fluorinated dioxole is perfluoro-2,2-dimethyl-1,3-dioxole.
 5. Acopolymer of perfluoro-2,2 dimethyl-1,3 dioxole and tetrafluoroethylene.6. A homopolymer of perfluoro-2,2 dimethyl-1,3 dioxole.